Modern photographic materials, particularly color negative films, contain a variety of so-called image modifying couplers including development inhibitor releasing (DIR) couplers, switched or timed inhibitor releasing (DIAR) couplers, bleach accelerator releasing couplers (BARCs) and colored masking couplers. DIR couplers, such as those described in U.S. Pat. No. 3,227,554, and DIAR couplers, such as those described in U.S. Pat. No. 4,248,962, perform such useful functions as gamma or curve shape control, sharpness enhancement, granularity reduction and color correction. BARCs, such as those described in European Patent Application 193,389, facilitate the oxidation of developed silver in bleach solutions. They may also enhance silver developability, thereby affecting gamma. Masking couplers, such as those described in J. Opt. Soc. Am, 40, 171 (1950) and in U.S. Pat. No. 2,428,054, are used to correct for the unwanted absorptions of various imaging dyes.
Modern color negative films often contain both image couplers, which contribute solely to the production of dye, and image-modifying couplers, such as those described above. The image-modifying couplers, in addition to having an image modifier component (e.g. bleach accelerator or development inhibitor), also comprise an image dye parent. In films which comprise both image couplers and image-modifying couplers, much of the ultimate color density exhibited by the film is often derived from the parent of the image-modifying coupler.
Many films today contain large amounts of such image-modifying couplers in the red-sensitive, cyan-dye-containing layers. These image-modifying couplers typically have cyan image dye parents which generate cyan dye upon reaction of the image-modifying couplers with oxidized developer. Because such cyan dye substantially contributes to the total red density in these films, it is important that the dyes generated from the image-modifying couplers have suitable properties. Desirable properties include good hue, good stability, resistance to reduction in seasoned bleaches or in bleaches of low oxidizing strength, and resistance to hue changes on storage at low temperatures.
Resistance to reduction in seasoned bleaches is particularly important because certain cyan dyes are prone to being reduced by ferrous ion complexes (such as ferrous EDTA) and other reducing agents, which are found in seasoned bleach solutions. When reduced, these cyan dyes form leuco cyan dyes (LCD formation). Leuco cyan dyes are colorless and, thus, films containing couplers which are easily converted into leuco cyan dyes exhibit substantial loss (and variability) in color density during processing.
Resistance to hue changes upon storage at low temperatures is also of particular importance. Certain cyan dyes tend to crystallize at low temperatures. This naturally affects the hue of such dyes, and it ultimately leads to inaccurate color and tone reproduction in films which have been stored at low temperatures, and which contain these dyes.
From the above, it can be seen that a need exists for image-modifying couplers which are capable of being used in conjunction with image couplers, and which can contribute substantially to the overall color density of an image. Furthermore, a need exists that the dyes generated from such image-modifying couplers be resistant to reduction in seasoned bleaches and be resistant to crystallization at low temperatures.
Certain of the above needs have been provided by known couplers having a 2-phenylcarbamoyl-1-naphthol structure. However, such couplers do not enable all of the above needs to be met. Image couplers, for instance, are known which yield dyes that are resistant to reduction in seasoned bleaches (U.S. Pat. No. 3,488,193 and U.S. Pat. No. 4,957,853). However, these couplers often crystallize at low temperatures. Furthermore, U.S. Pat. No. 4,957,853 discloses that these couplers should not be combined with photographically useful groups to form image-modifying couplers. Such a combination would impair the photographic properties of a photographic element containing the image-modifying couplers.
Bleach accelerator releasing couplers, development inhibitor releasing couplers (both timed and untimed, switched and unswitched), and masking couplers, having a 2-phenylcarbamoyl-1-naphthol structure, are also known (EP 0193389, Japanese Kokai JP62-247363, U.S. Pat. No. 4,725,530, DE 2,454,329, British Patent 1,111,342, Japanese Kokai JP62-087959, U.S. Pat. No. 3,459,552, and U.S. Pat. No. 4,883,746). Several of these image-modifying couplers, however, provide dyes which crystallize at low temperatures. Several others provide dyes which are prone to reduction in seasoned bleach, or which exhibit improper hue; and still others have insufficient or improper image-modifying effect.
As noted, a need exists to provide for image-modifying couplers which are capable of being used in conjunction with image couplers, and which can contribute substantially to the overall color density of an image. Furthermore, a need exists that such image-modifying couplers be resistant to reduction in seasoned bleaches and be resistant to crystallization at low temperatures.